Charles Lindsey's Home Page

So who is Charles Lindsey?

Oh! I thought you knew that! Why else are you looking here?

OK then, here it is.

I used to be a Senior Lecturer in the Department of Computer
Science at the University of Manchester (and before that I worked for
Ferranti/ICT, and before even that I was a Research Student at the
Mathematical Laboratory in Cambridge). In September 1992 I took Early
Retirement, with the grand title of "Honorary Fellow"
(which means whatever I want it to mean).

And I also brought home my SPARCstation, so that I could continue
to do interesting things on it.

My interests

Well, everything to do with computers really, but particularly
with how to make them do what you want. Hence my particular interest
in Programming Languages, and in one language in particular:

ALGOL 68

"The Language that Never Was", as some might say. But it
was used for productive programming, and it established many
ideas now familiar in later languages (Pascal, C, C++, SML, Ada).
Although I was not involved in the original development of the
language, you will find my name amongst the Editors of the Revised
Report, and as an author of its Informal Introduction. For the full
gory story, see my paper in History of Programming Languages-II
(ACM Press).

And I can still provide you with my own ALGOL
68 compiler, if you want to have a play. Or, for other compilers,
see Malvern's free A68->C
offering (actually, it is hidden inside a package called "Ella"
which is written using it, but it is not hard to disinterr it). Or
you could try the Peter
Craven / David Lloyd offering (not free AFAIK) which runs on PCs
under various systems (notably OS/2) and also under SPARCs under
SUNOS4. And there is also another Algol 68 to C compiler
available from Sian
Leitch and an interpretive one from Marcel
van der Veer.

Domains and Powerdomains

Not that I am interested in Denotational Semantics as such, but I
want to talk about the Semantics of Specification Languages where
nondeterminism plays a large role - and particularly unbounded
nondeterminism. Which is where conventional Domain Theory lets me
down because it imposes all sorts of restrictions which, according to
my Gut Feeling, are unjustified.

It is my belief that Domain theory can be formulated in a much
simpler manner. But to prove that I need to understand the
conventional treatment, and that is hidden away, behind a mountain of
mumbo-jumbo in unreadonable papers, and even more unreadable
textbooks. I believe I now see how to do it, but don't hold your
breath just yet.

Computer Conservation

I have been taking an active interest in Hartree's Differential
Analyser, a mechanical analogue machine built in 1936, part of which
is on display in the Museum of Science and Industry in Manchester. In
1994, I did a survey of the machine with a view to having it restored
to working order; I was thanked politely, but no it is not "our
policy" to restore it. I5 years later, they suddenly changed
their tune, and I have been leading a CCS working party to get it
running since 2010. You can see the results or our endeavours here
and some slides relating to the movie "When Worlds Collide"
from a talk I gave here.

Usenet UK

I have been an avid reader of Usenet newsgroups for many years. It
is my firm belief that they are a Good Thing.

In early 1995, when the present explosion in Internet Connectivity
was taking off, the uk.* hierarchy was in a
shambles. It was originally the creature of Uknet, which was fine
when they were the only ISP around. Now everybody was in on the act,
people were clamouring for more groups, but there was noone to decide
what was, and what was not, an "official" newsgroup within
uk.*. Everybody was talking, but nobody was actually
doing anything, and new and worthwhile groups were not
getting created.

So I decided to do a bit of Banging Together of Heads. I set up a
mailing list known as 'Newscoord' of people who seemed willing to
look at the problem seriously, and I got the three main UK ISPs (now
four) on board. Then we produced some Guidelines, and a Voting
procedure, and a suggestion for a Committee to oversee them. And we
put it all before the readers of uk.net.news where,
after much debate and argument, the proposals were voted on and
adopted by a substantial majority.

So now the uk.* hierarchy is run by this
Committee, of which I am a member (having recently been re-elected to
a fourth three year term). And now the uk.*
hierarchy is strong and healthy, and growing like Topsy.

I became interested in matters relating to the various stages of
the Government's attempts to gain access to encrypted communications
which lawfully came into its possession as a result of my membership
of the UKCrypto
Mailing List, and I submitted my comments to the various
consultative documents as they appeared, for example Comments
on theDTI
proposals.

When the Bill was finally published, I prepared a series of
Scenarios to expose the weakness of that
Bill. The particular version you will see by following that link was
produced as the Bill entered the House of Lords, and it has now been
somewhat overtaken by events (and most of its links no longer work).
I worked closely with various member of parliament, in both houses,
and prepared many amemdments. Whilst these amendments did not
directly affect the form of the Bill, the collective furore created
by my colleagues on the UKCrypto list and by others involved as ISPs
of as practitioners of E-Commerce was effective in persuading the
Government to make signficiant changes to the Bill (notwithstanding
which, the Act as finally passed is still a Dog's Dinner).

Other documents produced during the course of the Bill's passage
include:

DKIM

DKIM is an IETF Working Group (see
http://www.ietf.org/html.charters/dkim-charter.html
which has produced a scheme for signing headers of emails of which I
have been somewhat critical. If you follow this
link you will find a program written in Perl to demonstrate how
their canonicalization scheme could be improved.

Other pages to look at

This is a record of my investigation into the source code of PGP
to see whether it contained any Trojan that might compromise the
security of the keys that it generates. I uncovered various oddities,
but nothing to compromise its basic soundness. It refers to version
2.6.3 of PGP, so it may be a little dated now.

Owners of PGP web pages, please feel free to
point at this (but check periodically that it is still there).

Software

ALGOL 68S Compiler

This compiler currently runs on

Sun3

Sun Sparc (under SUNOS 4.1)

Sun Sparc (under Solaris 2)

Atari ST (under GEMDOS)

Acorn Archimedes (under RISCOS)

and it could easily be made to run under Linux if someone will
kindly volunteer to do a little hacking (not much).

For years I have been using Sun hardware running the Solaris
operating system, and have been using the secondary selection,
an established feature of X-Windows, when editing texts. On switching
to Linux in X86 hardare, I was horrified to find that this feature
was not supported, so I set about hacking the GTK+ toolkit to rectify
this state of affairs. Click the link to find out more.

CNEWS patches

There are two lots of patches here. One to implement the PGP
checking of control messages, as now used by most authoritative
issuers of newgroup, rmgroup
and checkgroups messages. The other makes
some minor further enhancements, such as updating altered newsgroups
file lines in newgroup and more intensive
checking of the format of checkgroups.